The long term objective of this work is to further our understanding of centrosome and spindle movements during cell division. Both mitosis and meiosis require a series of highly orchestrated microtubule (MT) based motility events now known to be powered by mechanochemical proteins. Many of the cell division motors identified thus far belong to the kinesin superfamily. In this study, Drosophila genetics will be used to study two different kinesin-like proteins or KLPs during both mitosis and meitosis. KLP urchin, which is required for the process of centrosome separation will be further analysed genetically. Since mechanistically little is known about this fundamental process, both a genetic and molecular screen will be used to identify interacting genes. These studies will reveal the molecular function of urchin as well as other essential genes that are required for spindle assembly. Urchin probably has a meiotic function as well since it is expressed during meiotic prophase. Meiotic spindle assembly differs dramatically from that of the mitotic spindle. The final structure and cell cycle arrest at metaphase are also unique features of meiosis. Proper maintenance of the arrested meiotic spindle is critical, considering that this configuration must be maintained for decades in humans. Without it, resulting chromosome loss can be devastating. Given the importance of this problem the association of urchin with the meiotic spindle will be verified using a newly developed high resolution immunolocalization technique. The next stage of this work will be a mutant phenotype analysis of urchin function during meiosis The second KLP that will be studied genetically is KLP67A. Both RNA and immunolocalization analysis strongly suggest a mitotic role for this KLP. KLP67A is not related to any of the known families of KLPs suggesting that is may perform a novel mitotic function. This is also evidenced by the association of this KLP with mitochondria as well as the endosymbiont Wolbachia on astral spindle fibers. The KLP 67A genetic analysis will therefore reveal a unique aspect of division. A further medical significance derives from the fact that Wolbachia are within the Rickettsiaceae family of bacteria. Certain members of this family cause serious diseases such as Typhus and Rocky Montain spotted fever. The mutant phenotype analysis of KLP67A will therefore be relevant to an understanding of arthropod vectors in the transmission of rickettsial diseases.